I've recently developed a 1.72 - 1.78 amp parasitic battery drain on my '03 GMC envoy. I've traced the draw to the HVAC-B fuse located in the under-seat fuse box. By pulling the HVAC-B fuse I can see on my multi-meter a gradual drop from somewhere in the 1.7 amp range to under 100 milliamps. With the fuse pulled the entire HVAC system is dead - not surprising. And with the fuse in the entire HVAC system functions just fine. I have no idea how many control modules are fed off this circuit but I'm assuming one or more of the control modules are not falling into sleep mode after the ignition is switched off. How do I isolate the parasitic drain any further? What modules might be suspect?